There has been conventionally executed a technique whereby a decorated molded product is manufactured by a transfer molding method wherein a decoration pattern on a transfer film held between fixed and movable molds is transferred through a transfer method to a molded object simultaneously with injection molding of the object. Since a resin is injected from the side of the fixed mold in the above technique, generally, the transfer film is held in tight contact with the movable mold, so that-the resin is filled between the transfer film and the fixed mold.
Meanwhile, in some cases, the resin is filled between the movable mold and the transfer film which is kept in touch with the fixed mold although the resin is similarly injected from the fixed mold as above. For example, as disclosed in the published specification of Unexamined Japanese Patent Laid-Open Publication No. 59-194848, holes are formed in the transfer film taken out from a coil and the resin is injected and filled from the fixed mold to a gap between the movable mold of a molding part and the transfer film through the holes of the transfer film. The holes of the transfer film are formed in any of the following methods: (1) A hole formation device is set in the fixed mold, and the transfer film is cut by a blade after clamping of the molds, whereby holes of a size passing the resin are formed; (2) The transfer film is pierced and broken by an injection nozzle after clamping of the molds; (3) The transfer film is pierced and broken with a pressure of the resin injected after clamping of the molds.
All of the above methods have problems.
Specifically, when the transfer film is cut, a large amount of cutting dust is mixed into the molten resin. The cutting dust is also accumulated thereby to clog an opening part of a runner. Moreover, the cutting dust is accumulated at parting faces thereby to damage the molds. Since the hole formation device is buried in the mold, the mold is complicated and bulky in structure, which miniaturizes a cavity. The method is poor in practical utility.
According to the methods (2) or (3), the transfer film is forcibly broken by the injection nozzle or molten resin, and therefore it is impossible to surely open small holes in the transfer film. Even when the hole is opened, a large broken tongue-like piece of the film tightly adheres to the movable mold, clogging the opening part of the runner in the movable mold and obstructing the molten resin in flowing.
An object of the present invention is to solve the aforementioned problems and provide an apparatus and a method for manufacturing decorated molded products whereby the generation of cutting dust is restricted and a small hole is surely formed in an insert film to pass a molten resin.